aclocal: Fix regression in linker detection
aclocal: Fix regression in linker detection

5ddb307edf15c4d86e5c35c4063ec967424e19f2 regressed autoconf's ability to
find the linker due to a silly variable interpolation issue, causing
segmentation faults on AArch64.

sdiehl/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc